The present application relates to semiconductor device fabrication, and more particularly, to a method of forming self-aligned middle-of-line (MOL) contacts using a raised metal semiconductor alloy.
Field Effect Transistors (FETs) are essential components of all modern electronic products. Generally, and after a transistor is formed, electrical contacts are made to connect a source region, a drain region, and/or a gate region of the transistor to make the transistor fully functional. In a conventional electrical contact forming process, contact via holes are typically formed using photolithographic patterning and etching. With the continuous scaling of device dimension in integrated circuits, the gate-to-gate pitch is getting so narrow that forming contact via holes between two gates using direct patterning becomes very challenging. Moreover, as the associated metal interconnection line patterns are miniaturized, the aspect ratio of via holes increases which makes completely filling via holes with a low resistance metal, such as tungsten (W), very difficult. Therefore, there remains a need to develop a method to form MOL contacts without the need of using photolithographic patterning and etching processes.